Mine fires constitute a significant threat to health and safety of personnel working in the underground environment, as well as pose environmental threats and risks to structures above ground in the vicinity of a mine fire. A variety of materials have been used to extinguish fires in underground mines and other confined areas. These materials include water, foam, and the like. While water can remove heat and deprive a fire of oxygen, the water often quickly evaporates before the fire is completely extinguished. Unless water is soaked into the material of the structure on fire, the water evaporates before the fire is extinguished. In addition, only a limited amount of water can even be absorbed into a structure on fire before it evaporates. Water may not readily soak into many structures and simply runs off and is unused. Therefore, a steady supply of water directed onto the fire is required. Significant manpower and a water supply are required to re-apply water and/or re-soak structures from which water falls off, or is evaporated, to provide continued fire protection.
Foams have been used in fire fighting in an effort to apply a more stable material that does not fall off or quickly evaporate. Such foams have been used to control fires in underground mines and other confined areas. In order to prevent the addition of oxygen into the location of a mine fire, nitrogen-expanded foams have been suggested as a fire suppressant in underground mines, as disclosed in U.S. Pat. No. 7,104,336. The area involved in a fire is contacted with a nitrogen-expanded foam that has smothering fire-extinguishing properties, as compared to conventional air-expanded foams. While a nitrogen-expanded foam has structural integrity that can fill a confined area and remain for a period of time in place on a structure, foams cannot flow into, or be pumped into, interstitial gaps within a structure on fire, such as into a coal pillar. Accordingly, while foams can be efficient for suppressing fire in an open area, their use in underground mines for extinguishing fires in a coal pillar, or within a coal stockpile, are limited.